The present invention relates in general to an apparatus for maintaining recreational or sports equipment and, more particularly, to a dynamic inertial balance apparatus for use in balancing recreational equipment such as golf clubs.
Many types of recreational or sports equipment such as golf clubs require balancing for optimal performance. Golf clubs typically come in a set with each club having a different length, head weight, head angle, etc. The golfer uses a specific club of choice for the shot at hand. An important aspect of successful golf play and lower scores is the repeatability of the golf swing which in part comes from an understanding of how each golf club will perform during the swing. By balancing the golf club set, the golfer gains confidence in knowing how each club will respond during the swing. The preferred scenario for most golfers is to have the ability to pull any club from their bag, swing their normal swing, and hit the ball near the intended target. Having one or more clubs which swing or perform significantly different from the other clubs is undesirable and can cause problems for many golfers.
In the prior art, a swing weight scale has been used to balance golf clubs. The amount of handle weight versus head weight is known as the swing weight. The swing weight method is a static measurement of the gravitational moment for a golf club pivoting about a fulcrum which, for many club designs, is located about 36 centimeters from the butt end of the club. To implement the swing weight method, the golf club is placed horizontally on a static balancing scale. The static balancing scale is adjustable so that the product of head weight times distance from the fulcrum to the center of mass of the head side of the club is equal to the product of handle weight times distance from the fulcrum to the center of mass of the handle side of the club. The adjustment feature of the static balancing scale adds weight, typically to the handle side of the fulcrum, to balance the gravitational moment of the golf club.
The swing weight method provides an indication as to the weight of the club head in relation to the weight of the handle end, i.e. head-heaviness or head-lightness. Each of the golf clubs in the set can be measured or tested to determine the variability over the set between head-heavy and head-light. Some golfers prefer that each club in the set possess the same gravitational moment, i.e. same swing weight for each club. Other golfers desire to establish a preferred and known profile of gravitational moments over the set. The optimal balancing of golf clubs is very personal for each user.
The static swing weight balancing scale takes into account the ratio of head weight to handle weight and distance from the fulcrum to the center of mass of each side of the golf club. Unfortunately, with the advent of new materials and designs in golf clubs, such as longer graphite shafts and greater variability in head weights, the balancing scale being a static measurement device does not accurately account for other important features of the golf club which affect its motion during the swing such as different materials, different lengths, and different mass distributions. For instance, two clubs can have exactly the same swing weight, but have dramatically different total weights or weight distributions which will result in significant variability in swing performance.
In one aspect the present invention is a dynamic inertial balancing system which comprises a base and a shaft mounted to the base with freedom to rotate. A rotational mechanism is coupled to the shaft to impart rotational torque on the shaft. A swing arm is adapted for mounting a golf club, oriented in a horizontal plane, and coupled to the shaft to cause the swing arm to traverse a
redetermined arc in the horizontal plane. The golf club is positioned a predetermined distance from the shaft to measure mass moment of inertia of the golf club as a function of time needed to traverse the predetermined arc.
In another aspect, the present invention is a golf club balancing system, comprising a base and a shaft mounted to the base with freedom to rotate. A rotational mechanism is coupled to the shaft to impart rotational torque on the shaft. A swing arm is coupled to the shaft and adapted for mounting a golf club with first and second brackets to cause the golf club to traverse a predetermined arc in the horizontal plane. A swing start mechanism detects the swing arm at a start position of the predetermined arc. A swing stop mechanism detects the swing arm at a finish position of the predetermined arc to measure mass moment of inertia of the golf club as a function of time needed to traverse the predetermined arc.
In yet another aspect, the present invention is a method of balancing a golf club, comprising the steps of mounting a first golf club to a swing arm connected to a shaft, applying a rotational force to the shaft to rotate the swing arm through a predetermined arc in a horizontal plane, starting a timer as the swing arm leaves a start position of the predetermined arc, and stopping the timer as the swing arm arrives at a finish position of the predetermined arc to measure mass moment of inertia of the golf club as a function of time required for the swing arm to traverse the predetermined arc.